Alekhine Defense: Modern Variation, Keres Variation

The Alekhine Defense: Modern Variation, Keres Variation is a chess opening classified under ECO code B04 in the Semi-Open Games family, where Black responds to 1.e4 with something other than 1...e5, including the Sicilian Defense, Caro-Kann, and Pirc. It is reached after 7 moves: 1. e4 Nf6 2. e5 Nd5 3. d4 d6 4. Nf3 g6 5. Bc4 Nb6 6. Bb3 Bg7 7. a4. The resulting position leaves black to move.